Good Speakers

What to expect from a good speaker? In reality, the question should be, what to expect from a good music playback system, as there are other elements besides the speaker. Traditionally, of course, the weakest link in the chain is the speaker. In any case, a good speaker is necessary for quality music playback.

First, it is necessary to distinguish the qualities, the absence of which makes a speaker bad, but their presence doesn't necessarily make the speaker good.

Frequency and Sound Pressure: The first such quality is the frequency and sound pressure, or simply the sound pressure curve. An ideal curve is a straight line (measured in an anechoic chamber, not at home). This straight line should cover the range of 30/40 - 19,000/20,000 Hz. There is no ideal world. In practice, there may be three problems with this curve: some part is missing, the curve is not straight, and there are significant irregularities on a micro level.

If any frequency range is missing, the situation is very bad. This cannot be compensated in any way. For example, when measuring an old computer speaker, it turned out that there was only noise above 10,000 Hz. Unfortunately, such a product ends up in the trash sooner or later.

If the curve is not straight, the system as a whole can often solve the problem. The speaker doesn't become unbearable for me if I have to turn up the bass knob on my amplifier a bit, and then everything is fine. Today's technology allows for noise and distortion-free correction of very specific sound anomalies if done digitally. However, care must be taken to ensure that the anomaly of the curve is not a fundamental problem that cannot be compensated (e.g., a design flaw in the crossover of the speaker, reaching the limits of the loudspeaker, a construction flaw, etc.).

Micro-level irregularities are mostly not audible, and you can live peacefully with such a speaker. If this micro-level irregularity is not exactly the most-used note in the sensitive range of hearing, you can hardly notice the presence of this fault. In most cases, these are rare, and the problem may be with a very special speaker where the solution used creates sharp peaks in some sound ranges (a hole is almost never audible).

So the potential of a good speaker exists in a speaker whose sound pressure curve is straight within the desired range or can be corrected with other components of the sound system.

Spatial Distribution of Sound Energy: The next important metric is whether the speaker sounds the same head-on and in all other directions. Sound waves want to spread spatially immediately after leaving the loudspeaker. If spatially, the sound pressure curve is analogous to the sound pressure curve in the front view, dropping in the high-frequency range, then all is well. For example, if it turn out that in other directions, the 1000 - 2000 Hz sound spreads significantly more there is problem. This means that at the listening position, due to reflections, the level of this sound range is stronger, and this peculiarity is impossible to reasonably correct. Direction is not so important for the initial assessment as the sum of all directions compared to the front view. Of course, the prerequisites for a good speaker are larger, and so the listening place could be wide enough, and the expansive sound profile would be uniformly equal in addition to no interference between loudspeakers.

Lack of Additives: I still have my very old Radiotehnika S70 speakers. Out of nostalgia, I connected them to an amplifier, and oh, surprise, the midrange loudspeaker produced resonances at relatively even intervals, at least at three frequencies. (I replaced it. Now I would need to replace the tweeter, redo the crossover, and it's a good speaker.) Of course, a speaker should not add sound independent of the music. It is not independent in the literal sense of the word, but it is unnecessary and unintentional. Naturally, no new speaker has such additives, but this topic needs to be addressed because there can be variations - very strong and audible harmonic frequencies are the most likely.

If these three qualities are fulfilled, we have at least a mediocre speaker. To make a good or excellent speaker out of a mediocre speaker, a long journey awaits, often in different aspects. The first sign of a good speaker is not related to sound at all.

Purposefulness. The Bowers & Wilkins Nautilus speaker is an excellent speaker, but it is probably not a good speaker for an office desk as a computer speaker. There may be doubts about whether it is good in any smaller room or whether I even have a room at home where I mentally fit in with it. This extreme example makes the expectation much clearer. When evaluating the suitability of a speaker, the first aspects are the desired listening distance, the width of the listening area, the dimensions of the speaker, the possibilities for placement, the desired sound level, and requirements for appearance. In example for me, the appearance is less important in the bedroom, but sound quality is more important than in the living room. Of course, the speaker is closer; of course, it requires a wide listening angle. Considering the time of day, there is no need for very low bass, and sound quality is needed at a lower volume. So, when evaluating each speaker, it should be taken into account where it is needed and from the opposite side what it is created for by the manufacturer.

Timing. If all sound frequencies are present but the sound is not synchronized, then there cannot be a great speaker. There are some discussions on the Internet about whether this can be heard and if it is heard, how it affects. Timing has a special case; it either exists or doesn't (if we are talking about ordinary home speakers, i.e., milliseconds and their tenths). If the speaker is not timed, then everything sounds the same. If it is timed, the soundstage becomes spatial and particularly clear. While the phase of the speaker itself can be precise here, we cannot talk about the sameness of music or the preservation of phase. In reality, none of us have seen what was done during recording and mixing. So in practical life, it is important that when moving from one loudspeaker to another, the sound does not shift in time relative to the other. In any case, the speaker's phase changes with frequency, and you can fight with the laws of physics, but generally physics tends to win.

Timing is most important in the frequency range where a person determines the direction and distance of sound. The higher the sound, the shorter the wavelength, and the more precisely the location of the sound source can be determined. However, in real life, very high frequencies are rare, so timing is more important for the frequency range where human hearing is most sensitive, and the wavelength is smaller than the distance between the ears. Surely the sound should be timed in the range of 800 - 6000 Hz. For example, in the filter frequency of a common two-way speaker, at 1500 Hz, a shift of 0.05 ms can be heard, and 0.2 ms is already beyond the timing window (there is no discernible difference if the shift is 0.2 ms, 0.3 ms or some other number).

When it comes to low frequencies, things are different. Timing the subwoofer's position at 80 Hz, you can hear a change in timing as a frequency graph shifts, but the timed bass itself doesn't raise eyebrows. Clearly, human hearing is not intended to determine direction or distance in this frequency range, so a subwoofer shifted from the right place doesn't bother as long as the entire sound profile is in place.

It's quite certain that people have varying spatial perception, which can affect the ability to hear timing.

Accuracy, Forgiveness, and Freedom are different vies of the same shape.

An accurate speaker faithfully reproduces every sound in an audio recording. This means that the speaker's diaphragms don't flex or have restricted movement, and they don't distort or soften the sound. If the sound is sharp, it remains so. However, when listening with an accurate speaker, defective moments of music recording become unbearable, even though every other moment of the music is excellent. Thus, an accurate speaker places high demands on the quality of the audio recording being listened to.

On the other hand, forgiveness, characterized sometimes as "soft bass" or "silky treble," refers to a more forgiving speaker. With a forgiving speaker, all the imperfections in the recordings are audible but not annoying. However, after experiencing an accurate speaker, you might want a good compromise where the flaws in the audio recording are forgiven, but everything else is accurate.

Freedom is the ability of a speaker to present sound without restrictions. This is a simple rule for the manufacturer but is more challenging for the listener to discern. Freedom means that the speaker's performance is consistent, and the limits of its capabilities are reached simultaneously or outside the listening range. If a loudspeaker is pushed to its limits, the sound is different; it becomes constrained. The speaker may not respond to changes in volume or dynamics of music or in extreme cases starts to distort the sound. If these limitations are at the very low or high end of the frequency range and do not result strong distortions, it merely means that the usable frequency range becomes narrower as the volume increases. If the natural roll-off is shifted slightly up or down, the speaker's sound doesn't change too much. It's worse when the loudspeakers are near their limits at the crossover frequency. Then, there's a problem in the middle of the sound image. While it's possible that all sounds are produced at all volumes, a speaker like this won't sound right.

Just as there can be many beautiful shapes, there can also be several beautiful combinations of precision and forgiveness. Depending on the music and the listener's expectations, it can be pleasant either with gentle softness or with a bright sharpness. And freedom is a clear optimization task. The cost of freedom is high; a truly free-sounding speaker is also truly expensive. However, if the speaker is intended, for instance, for quiet evening listening in a bedroom, it's worth pondering whether it's worth the investment for the level of freedom that extends to ear-piercing volumes. 

Magic. Going beyond the typical sound pressure profile, a great speaker should be able to perform magic, captivating the listener into a concert hall where music is experienced authentically. Returning from the world of fairy tales to reality, this requires good match of the speaker and the room. High-quality sound reproduction is a prerequisite because discrepancies will bring the listener back to reality. This has also some technical prerequisites, but they're not promoted by any manufacturer. Achieving this kind of magic isn't easy, requiring a sparkle between capable speaker, listening room, and the listener.

The last essential characteristic of a speaker is the absence of prejudice. When a speaker looks at someone, it decides to present exceptionally poor sound to them, as having a bias toward that listener. Oops, I think that went the wrong way. Prejudice is still with the listener. Sound quality is always a combination of the listener, the room, and the audio system. The listener's bias is one part of the sound picture. There are some word descriptions for speakers and other audio equipment. It's not worth believing in them too much or being stuck with them. A silk diaphragm tweeter can be accurate if it has a lot of freedom. Similarly, an aluminum diaphragm bass loudspeaker can be forgiving if it has this type of motor. The speaker with the straightest sound profile can fall short compared to others in listening tests, etc.

Buying speakers remains an experimental science. The prerequisite for a successful experiment is to consider the purpose and characteristics of the speaker beforehand and select the speaker accordingly. Contrary to the common belief that you should listen to speakers before buying, I recommend purchasing speakers online. First, no listening session in a store or showroom can give you an accurate idea of how the same speaker will sound in your own room at home. Second, when you make a purchase online, you have a return policy. It's important to take this seriously, protect the speaker from any damage, keep the packaging, and if you don't like the speaker, you can return it accordingly.